Metabolism Overview

Introduction to Metabolism

• Metabolism involves breaking down food to extract energy and building blocks for the body.
• Organic molecules from digestion are distributed to cells.
• Cells utilize these molecules for building larger compounds (anabolism) or breaking them down for energy (catabolism).

Cellular Functions and Energy

• Cells use nutrients to maintain homeostasis and perform essential functions.
• ATP (adenosine triphosphate) is the main energy source for cellular processes.
• Oxygen is essential for ATP production through mitochondria.
• Metabolism includes both cellular metabolism and overall body metabolism.

Nutrient Sources

• Carbohydrates, Fats, and Proteins are the primary macronutrients.
• These nutrients are broken down into simpler forms to generate ATP.

Anabolism and Catabolism

• Anabolism: Building larger molecules like proteins and lipids for maintenance and growth.
  • Uses energy.
• Catabolism: Breaking down molecules to produce energy (ATP).
  • Releases energy.

Energy Storage and Usage

• Triglycerides: Storage form of fatty acids. Checked for health reasons (heart disease risk).
• Glycogen: Storage form of glucose for quick energy release.
• No specific storage form for proteins; excess use can reduce muscle mass.

Molecular Composition

• Glucose Molecule: C₆H₁₂O₆ (6 carbons).
• Fatty Acids: Carbon backbone, more hydrogens than glucose.
• Amino Acids: Have a nitrogen group, distinct from carbohydrates and fats.

ATP and Cellular Processes

• ATP is required for various cellular activities such as growth, secretion, and contraction.
• Even resting cells require ATP for basic functions.
• Higher energy needs for organisms that maintain constant body temperature (e.g., humans vs. reptiles).

Metabolic Pathways for ATP Production

• Glycolysis: Initial step in glucose metabolism; occurs in the cytoplasm.
• Citric Acid Cycle (Krebs Cycle): Occurs in mitochondria; requires oxygen.
• Electron Transport Chain: Also occurs in mitochondria; produces the bulk of ATP.

Photosynthesis and Metabolism

• Plants reverse the process of metabolism by converting CO₂ and water into glucose and oxygen.
• This symbiotic relationship highlights the importance of plant life for oxygen supply.

ATP Yield from Glucose

• Breakdown of one glucose molecule can produce up to 36 ATP molecules via aerobic respiration.
• Pathway includes glycolysis, the Krebs cycle, and the electron transport chain.
• Glycolysis alone can produce 2 ATP if oxygen is not available.

Conclusion

• Metabolism is critical for maintaining energy levels and supporting cellular function.
• Understanding the processes helps illustrate the body's need for nutrients and oxygen.